Field of the Invention
The present invention relates to a control device, an actuator including a control device, an image blur correction device, a replacement lens, an imaging device and an automatic stage. Specifically the present invention relates to a control device, an actuator including a control device, an image blur correction device, a replacement lens, an imaging device and an automatic stage capable of driving a moving body multidirectionally by synthesizing driving forces of a plurality of motors.
Description of the Related Art
Conventionally proposed actuators enabling multidirectional driving (hereinafter called, a multi-degree freedom driving device) include a device implementing XYθ driving using a linear actuator (Japanese Patent Application Laid-Open No. 2009-225503).
FIG. 10A shows the structure of a conventional multi-degree freedom driving device.
A base plate 1 is a base of this multi-degree freedom driving device, and vibrators 2, 3 and 4 drive a moving body 5. A position sensor 6 detects an X-direction position, and position sensors 7 and 8 detect a Y-direction position.
FIG. 10B is a side view of the device.
The vibrators 2 (not illustrated), 3 and 4 each include a vibration member (the upper part, of the vibrator 3, 4) having one protrusion and a piezoelectric element (shaded area), which are integrated by bonding or the like, and are attached to the base plate 1 via a not-illustrated attachment member.
Scale parts 6′, 7′ and 8′ are provided at a face above the position sensors. For instance, as the scale part 6′ moves in the X-direction, the sensor 6 outputs a positional signal corresponding to the movement amount.
The sensor 7 and the sensor 8 output positional signals corresponding to the movement amounts of the scale part 7′ and the scale part 8′ in the Y-direction, respectively.
This configuration moves the moving body in the direction that is a vector-synthesized direction of the driving forces of the vibrators 2, 3 and 4.
Japanese Patent application Laid-Open. No. 2009-225503 proposes a control system of a vibration type multi-degree freedom driving device shown in FIGS. 10A and 10B, and proposes a control method to correct variations of the individual vibration type motors. The control system includes a controller configured to perform PID control individually for a plurality of vibration type motors. That is, the conventional controller transforms position command values of XYθ into each motor movement amount, and then makes PID compensators individually provided perform position control.
FIG. 11 shows a control system of a conventional multi-degree freedom driving device.
The following describes the case of using the vibration type multi-degree freedom driving device shown in FIGS. 10A and 10B. A controller not illustrated gives position commands X, Y and θ, which are input to a motor coordinate transformation unit 1101.
The motor coordinate transformation unit 1101 deals with three vibration type motors (three vibrators) M1, M2 and M3, and includes a M1 coordinate transformation unit, a M2 coordinate transformation unit and a M3 coordinate transformation unit.
This unit transforms the position commands X, Y and θ into values on the coordinate positions where these vibration type motors are disposed, and the values depend on the directions of the position commands X, Y and θ and angles of vectors generating driving forces of the motors.
Herein, the transformation in the θ direction has to be performed while considering a relative position of each motor from the center of the moving body.
For instance, when receiving position commands XYθ, the X-direction instruction value of the M1 coordinate transformation unit is a position command value on the coordinates of the vibration type motor M1 and the Y-direction component thereof is zero when the θ direction is ignored.
Similarly, the instruction values in the X, Y and θ directions for the vibration type motors M2 and M3 also are allocated depending on the relationship of angles with driving vectors.
Meanwhile, detecting positions X, Y and θ obtained by a XYθ coordinate transformation unit 308 are input to the motor coordinate transformation unit 1101 and are transformed into values on the motor coordinate positions.
Then, the position commands and the detecting positions that are transformed into the three motor coordinate positions are input to a deviation calculating unit 1102 for calculation of a difference. This is position deviation of each vibration type motor.
Next, the position deviation of the three vibration type motors is input to a PID compensator 1103. The PID compensator 1103 includes three PID compensators, each of which is provided to control the corresponding vibration type motor.
Herein, when the three vibration type motors have the same driving force, identical control gain is set therefor basically.
Then, control signals for the vibration type motors output from the PID compensator 1103 contain information such as a frequency, a phase difference and a pulse width, which become driving parameters, and the control signals are input to a pulse generator 304.
Pulse signals output from the pulse generator 304 are input to a driving circuit 305, from which AC voltage of two phases which differ in phase by 90° is output.
The AC voltage output from the driving circuit 305 is applied to the piezoelectric elements of the vibration type motor 2, 3 and 4 (hereinafter called M1, M2 and M3), so that the moving body 5 operates in the vector-synthesized direction of the driving forces of M1, M2 and M3.
The operation of the moving body 5 is detected by the position sensors 6, 7 and 8, and a position detecting unit 307 performs arithmetic operation of positional information at each sensor position as X1, Y1 and Y2. The positional information X1, Y1 and Y2 is input to the XYθ coordinate transformation unit 303 and undergoes coordinate transformation as positional information of X, Y and θ.
In this way, feedback control is performed for the individual motors by the PID compensators so as to bring close to the position commands X, Y and θ.